Your power supply isn¬ít strong enough. Did you buy your computer, or build it yourself? A common problem from people that choose to build their own computers is that they use the stock PSU's that came with their case, which are ALWAYS underpowered. A reliable and inexpensive PSU is the ThermalTake TR2. Its 430W (+3.3V@20A, +5V@30A, +12V@18A, -5V@18A, -12V@0.5A, +5VSB@0.8A)--which is ok. I have one in my system, and since I got it in august, I haven't had a lockup or hardware related crash since. It is the best bang-for-the-buck PSU out there.